The present invention relates to a technology being useful in forming a large sized image in composing video signals of more than two.
Recently, it is known to the public to form a large sized image on a screen by using a plurality of projectors to display split images in making them be adjacent to each other in generating video signals corresponding to respective parts of an image split into predetermined areas.
FIG. 6 shows a drawing for explaining an example of an image display system using a soft edge matching device (hereinafter referred to as SEM device taking the first letters of the device) which enables to form a good image in correcting the joint (overlapped areas) of respective split images when the images are displayed being adjacent to each other.
As shown in FIG. 6, for a video signal source 50 for forming a composite image, for example, a personal computer device 51, a work station system 52, a hard disk data base device 53, a video playback device 54, or other variety of playback devices can be used. It is also possible to form split images from the image photographed by a video camera, or the like as photographing means though they are not shown in a drawing. These playback devices are typically shown in parallel in FIG. 6; however, all of them are not necessarily needed, and each device can be individually used or a plurality of them can be simultaneously used.
It is also possible to form a video signal source 50 with one unit of a playback device such as a hard disk data base device 53, a video playback device 54, or the like, and a video signal output from one unit of equipment is stored once as video data in the computer device 51 or the work station device 52, and by splitting an image on the screen, a plurality of video signals are generated corresponding to the split images, and output them as R, G, B component signals. In this case, a synchronizing signal can be superposed, for example, on a G signal or it can be treated as a separate signal and output through a cable to be solely used by it.
The plurality of video signals corresponding to the split images output from the video signal source 50 are respectively supplied to the SEM device 60. The SEM device 60 performs signal processing for a plurality of signals to make the overlapped areas corresponding to the end parts of respective images (joint parts of divided images) be continuous, and supply them to the projector devices, 70A, 70B and 70C, corresponding to the plurality of split images. FIG. 6 shows a plan view showing three projector devices; however actually there are provided projector devices corresponding to the number of video signals (number of split images) supplied from the video signal source 50.
The signal processing in the overlapped areas is executed by the operation of various kinds of operating keys disposed in the remote controller 61.
The projector devices 70 (A, B and C) convert the video signals to projection images with ordinary cathode ray tubes of high luminance, and project the images as a composite image on a screen 80. It is possible to constitute the projector devices 70 (A, B and C) with liquid crystal projector devices.
FIG. 7 shows, for example, images A and B, as two split images being disposed adjacent to each other in the horizontal direction, and a typical drawing for explaining an example displaying adjacent end parts being overlapped, and the screen 80 shows a case where the projected image A and the image B are disposed being adjacent to each other.
The adjacent parts of the image A and the image B, that is, the joint part is the overlapped area Q where the images are overlapped, and in the overlapped area Q, it is a prerequisite that the video signals are supplied to make the image A and the image B the same image. For such a video signal, an image may be produced considering the adjacent parts before hand, or the adjacent parts may be formed for an existing image with a personal computer device 51, or the like.
In FIG. 7, the video signals corresponding a horizontal period of the image A and the image B are shown as a video signal VA and a video signal VB, and the area hatched with the lines downward to the right corresponds to the overlapped area Q. Therefore, the video signal VA and the video signal VB comprise the information which makes it possible to form the same image in the overlapped area Q. Thereby, an image having no joint visually can be displayed.
However, in the Q area, even though the same video is formed and a desired image is formed, since a plurality of video are overlapped, the luminance becomes high partially, and it is needed to perform the luminance correction. Therefore, in the case of the video signal VA or the video signal VB, the correction starting point AE and the correction end point BS are set and the signal processing is so performed that the luminance level between the above-mentioned two points, AE and BS, of the video signal VA has a fade-out characteristic and that of the video signal VB has a fade-in characteristic. The overlapped area Q shows an area where the same video is to be formed, so that the correction starting point AE and the correction end point BS do not always coincide with each other.
In short, when two images are projected on the screen 80 using two units of projector devices 70 after the signal processing (luminance correction process) as mentioned in the above, the luminance level in the overlapped area Q of the screen 80 becomes the same level as those of the other parts in the image A or the image B, and the joint of these two images becomes unnoticeable.
Since the overlapped area Q shows an area where the same image is to be formed, the correction starting point AE and the correction end point BS do not always coincide with each other. When an area close to the left end of the video signal VA is made to be an over-scan area OS and an area close to the right end of the video signal VB is also made to be an over-scan area OS, it is possible to prevent the appearance of the edges of the image A and the image B on both ends of the screen 80.
Further, for example, when a composite image is displayed with three units of projector devices 70, video signals, Va and Vc, (Only those in a horizontal period are shown.) on the left and the right sides as shown in FIG. 8 correspond to the video signals, VA and VB. In the case of a video signal Vb to form an image in the central part, the end area `ae` of the video signal Va and the starting area `bs` of the video signal Vb are made to be an overlapped area Q. The end area `be` of the video signal Vb and the starting area `cs` of the video signal Vc are made to be an overlapped area Q, and the signals there are processed to be the same video signals.
Then, in these areas the fade-out process and the fade-in process are performed, and it is possible to perform the luminance correction of the edge parts of the images at the two boundary parts produced when three images are placed to be adjacent to each other.
In the prior art, it is arranged that the position setting of the correction starting point and the correction end point is performed for the waveform data to be corrected being set beforehand in the SEM device 60 and the desired correction data are calculated in performing a predetermined process based on the positions of these points. And the image status in the overlapped area Q is improved by superposing the calculated correction data on the video signal.
Therefore, the SEM device 60 has to perform an operational processing for obtaining the correction data, thus a control means is burdened to perform the operational processing.
For example, there is a method known to the public in which a detailed setting is performed using a computer, or the like and even fine adjustment is possible. However, there remains a problem that the operation to perform such a detailed setting is troublesome and an optimum correction data is not easily obtained.